In the old Cyberpunk 2020 the amount of implants any given character could have had a money cost, a healing time... and a "humanity" cost. The less human a character became, the more like a cold fish without emotions he was... until humanity 0, where the "cyberpsicosis" limit was reached. In Shadowrun, the implants "killed" the soul of the character, so being heavily augmented was equal to be like a zombie. Of course, if a limitation in this way is implemented (quite easy to derive from the Savvy value of the ego, for example -1 to Savvy per 5.000 creds of implants, not counting the ones that come with the body), one has to consider some stuff those two games didn't had to deal with, being it the change of body (and one CP and EP have in common, psicological treatment. In CP 2020, the only way to regain the humanity was to receive the treatment after the removal of the implants, while in EP we have psichosurgery... and the possibility of changing to another body... or using a forked infomorph of yourself for those pesky Networking rolls...). Personally, I limit the implants with a very simple rule: military-grade hardware is never looked like lollipops are, so where Reapers are forbiden, certain implants are, at least, controlled by security forces, and all morphs are scanned upon boarding on certain places (like Planetary Consortium controlled habitats)... which doesn't forbid the players to try to hide the implants, or bribe the guards... But as always, they risk being forced to sleeve into another morph if they still want to go in that habitat.

The implant interactions should be left entirely as a narrative tool, I think, because it would promote too much synthmorphs, and while we all agree that (on paper) a synthmorph is much better than any biomorph of comparable cost (another thing entirely would be the effects on the mindof the sleeved character... the first Takeshi Kovacs book shows that when presenting a woman trapped inside a case), part of the setting is that people prefers biomorphs to synths. Also, while a cyberbrain is better than a biobrain, it's also easier to hack and infect (basilisk hacks make possible to attack a biobrain... but in theory only TITAN-level of tech allow such technique). As has been said, making interactions between implants the matter of "what you can have and what you can't" leaves some players behind, and focuses another players into justifying their implants instead of playing the game. Forcing egocasts and visits to zones that require subtle augmentations, however, is much more equal to all players and requires less work from the GM, who only has to say "this habitat forbids those implants. You can get a software inhibitor, sleeve into another morph... or not go at all". Paranoid players should be right about refusing any PC controlled habitat to install software in their morphs...

Axel wrote:

... one player is literally sleeved in a battle-tank...

If he has lots of hardware he could run into problems with bad drivers! *ZING*

I've been playing around with a similar concept for our campaign, since I'd like to try and keep my players a little more grounded - at least for now - without discouraging them from being creative with modifications; I'm very much on the Call of Cthulhu end of EP than the players-are-walking-tanks action end of EP. We've yet to start but just going over the list with my players has me angsting about how, or even if, I should deal with souped-up morphs. One idea I've been thinking about, based on Arenamontanus's article on the subject, is essentially similar to the bad luck trait; every time the amount of extra implants (above the amount that morph gets by default) exceeds the morph's Wound Threshold, the GM gets a moxie point every session to use only with fritzing that player's enhancements in a creative way; their enhanced vision gets interference from their eelware, or their cyberware limb has problems interfacing with the character when they're using their Multi-Tasking implant. This has the nice added effect of only cropping up when players are actually using their implants in an active way, too.

I would let characters use most augmentations, psi sleights and other gifts with few limitations, in particular since I assume egocasting is the default travel option for most Firewall groups unless they mostly play in a single small region (Luna, Mars, Venus, Extropia, Titan, etc) or are involved in Gatecrashing. Further, most habitats will have *some* restrictions on the most egregious weapons and vehicles, and may object to over-the-top military enhancements. Either situation filters out excessive technological advantages. Biologically, unless I really think a set of augments are apt to interact badly, or that one or more might be badly implanted, I would let most things slide. Remember, the technology is very well-researched at this point, especially for standard, low-cost options. In particular, any set of modifications inherent to a common morph I assume to have no normal side effects other than any already stated for them (such Neurastem 2). There are two main issues with dramatically excessive augmentation. The first is the common, emergent Seed AI/Exhuman concern -- that characters might experience a runaway evolution, not necessarily of a positive nature, and end up as something both more and less than human. Or simply more. Or simply less. Or simply *Other.* The second issue is that I treat many augments and psi sleights as creating vulnerabilities to certain kinds of basilisk hacks aimed at advanced intelligences that are often completely ineffective against ordinary transhumans. For example, most mathematical enhancements render beings potentially vulnerable to hacks with a mathematical element, including certain programs that unfold over time given the correct formula supplied to the host mind -- piece by piece -- in concert with the correct data/stimuli. Any form of perfect memory (even, manipulated correctly, a Muse or common Mesh reminder programs) is an invitation for a hack to unfold over vastly greater timescales -- days, months, even years or longer. Grok enables the transfer of a vast multitude of relevant concepts and stimuli, without the targeted mind ever being aware of them. And so on and so forth. This quirk is a common issue for most emergent posthumans, especially as I treat many psi sleights as gifts potentially available to sufficiently developed intelligences, in particular nascent Seed AIs. And there is one final problem with being incredibly intelligent in Eclipse Phase, a being far more advanced than most of the very capable people all around you: You're actually interesting enough to attract this kind of attention in the first place. Your average engineer or security guard is not.